The HST survey of Magellanic-Cloud clusters and of their stellar populations

TL;DR

This paper reviews Hubble Space Telescope observations of Magellanic Cloud clusters, highlighting complex stellar populations and discussing possible causes like prolonged star formation, stellar rotation, or binaries.

Contribution

It provides observational constraints on the complex CMD features of young and intermediate-age clusters in the Magellanic Clouds.

Findings

Presence of bimodal or extended main-sequence turn-offs.

Detection of dual red clumps in intermediate-age clusters.

Broadened or split main sequences in young clusters.

Abstract

A large number of intermediate-age (~1-2-Gyr old) globular clusters (GCs) in the Large and the Small Magellanic Cloud (MC) exhibit either bimodal or extended main-sequence (MS) turn off and dual red clump. Moreover, recent papers have shown that the MS of the young clusters NGC1844 and NGC1856 is either broadened or split. These features of the color-magnitude diagram (CMD) are not consistent with a single isochrone and suggest that star clusters in MCs have experienced a prolonged star formation, in close analogy with Milky-Way GCs with multiple stellar populations. As an alternative, stellar rotation or interacting binaries can be responsible of the CMD morphology. In the following I will summarize the observational scenario and provide constraints on the nature of the complex CMD of young and intermediate-age MC clusters from our ongoing photometric survey with the Hubble Space Telescope.